The present invention relates to medical devices for delivering endoprostheses to predetermined treatment sites within body cavities or lumens, and further deploying the endoprostheses at the selected sites. More particularly, this invention relates to such devices that are capable of enabling or facilitating a tracking of the endoprostheses during deployment.
A variety of patient treatment and diagnostic procedures involve the use of prostheses inserted into the body of a patient and intraluminally implanted. Percutaneous translumenal coronary angioplasty (PTCA) and other vascular treatments frequently involve implanting prostheses such as stents to maintain vessel patency or grafts to shunt blood. Similar implantations are used in non-vascular procedures, e.g., enteral, billiary, and esophageal applications.
There is a need to accurately characterize the intended implant site to facilitate proper placement of the prosthesis. There is a further need, just before deployment and during deployment, to ascertain the location of the prosthesis relative to the intended placement site. One known approach to such characterizing and monitoring is angiography, which involves supplying a radiopaque contrast fluid to the cavity or lumen, then radiographically viewing the lumen. This approach, however, provides only a monochromatic, two-dimensional image showing a profile but no depth of field.
According to another approach, radiopaque markers can be placed on the delivery/deployment device. Before deployment, the position of the prosthesis within the device is known, and determining the device position in effect accurately determines the prosthesis position. This advantage is lost during deployment, however, and again the image offers neither distinctions in color nor depth of field.
According to yet another approach, the prosthesis can be fabricated at least in part using a radiopaque material. For example, the filaments of a stent can be formed of, or may incorporate a core formed of, platinum, tantalum or another radiopaque material. This approach likewise lacks the capacity for distinction among colors, and imposes limitations upon the materials used to form the prosthesis.
U.S. Pat. No. 5,411,016 discloses an intravascular balloon catheter having a lumen containing an angioscope. A distal portion of the catheter shaft, surrounded by the dilatation balloon, is transparent, and index markers are provided along the balloon. Thus, objects against which the balloon wall is pressed when the balloon is inflated can be quantified. This structure requires viewing the lumen through the catheter wall and the balloon wall, and does not address the need for monitoring the position of a prosthesis with respect to its delivery device during deployment. This need is particularly apparent in connection with radially self-expanding prostheses, which are constrained in radially reduced configurations during delivery, and must be released from their confining devices during deployment to permit radial self-expansion.
Therefore, it is an object of the present invention to provide a prosthesis delivery and deployment device that substantially surrounds a prosthesis to retain the prosthesis during delivery to a treatment site, yet facilitates an optical viewing of the prosthesis before and during its deployment.
Another object is to provide a prosthesis delivery device particularly well suited to negotiate tortuous intraluminal pathways in the body, that incorporates a translucent carrier segment through which a prosthesis carried within the device can be optically viewed.
A further object is to provide a process for deploying a radially self-expanding prosthesis within a body lumen in which an optical viewing device is advantageously used to view at least a proximal portion of the prosthesis to visually monitor a location of the prosthesis during its deployment.
Yet another object is to provide a catheter or other device for intraluminal delivery of a prosthesis, that incorporates a prosthesis confining wall sufficiently light transmissive to enable a viewing of the prosthesis through the wall, so that an optical instrument positioned within a body lumen outside the catheter can be used to observe the prosthesis contained in the delivery device, as well as tissue surrounding the delivery device.
To achieve these and other objects, there is provided a prosthesis delivery and viewing device. The device includes an elongate, flexible catheter having a tubular catheter wall defining a catheter lumen. The catheter, along a distal end region thereof, is adapted to substantially surround a body insertable prosthesis and thereby releasably retain the prosthesis within the catheter lumen. The catheter wall, at least along the distal end region, is translucent to allow an optical viewing of the body insertable prosthesis through the catheter wall when the prosthesis is so retained.
Most preferably, the distal end region of the wall is substantially transparent, i.e., highly transmissive of wavelengths in the visible spectrum. Satisfactory viewing is achieved, if the distal end region wall merely is translucent; more particularly, sufficiently light transmissive so that at least about 25% of light impinging directly upon one side of the catheter wall is transmitted through the wall to the other side. A polyether block amide, for example as sold under the brand name Pebax, has been found to be well suited as a catheter wall material, not only due to its relative transparency, but also because it provides a ductile or flexible catheter wall that bonds well with other polymeric material. Certain nylons also can be used, although they are not as ductile as the Pebax material.
The device is advantageously used as part of a system that also includes an optical viewing device positionable proximate the distal end of the catheter to facilitate an optical viewing of the prosthesis and surrounding body lumen or cavity. An endoscope is suitable as such viewing device.
According to one particularly preferred construction, the catheter includes an elongate, flexible translucent inner tubular body. A flexible, translucent first outer tube surrounds and is integral with a distal end region of the inner tubular body. An elongate, flexible second outer tube surrounds the inner tubular body, is integral with the inner tubular body, and is disposed proximally of the first outer tube. If desired, a flexible third outer tube is disposed between the first and second outer tubes, and contacts the other outer tubes to provide a substantially continuous profile composed of the three outer tubes. This construction allows a tailoring of the catheter, to provide a balance between two somewhat conflicting needs: sufficient flexibility to negotiate serpentine pathways; and sufficient columnar strength along the catheter length to provide the necessary axial pushing force.
In particular, such tailoring can involve selecting materials of different durometer hardness for the outer tubes. One highly preferred example uses a 63 Shore D durometer Pebax material in the first outer tube, and a 72 Shore D durometer Pebax material in the second, proximal outer tube which comprises most of the catheter length. To provide further columnar strength and resistance to kinking, a support structure can be interposed between the inner tubular layer and at least the second outer tube. A preferred structure is a braid of helically wound metal filaments, e.g., stainless steel or a cobalt-based alloy such as that sold under the brand name Elgiloy. If desired, the wire braid can extend distally beyond the second outer tube, and thus reside between the inner tubular layer and a proximal portion of the first outer tube, up to about one-half of the first outer tube length. When a third, medial outer tube is employed, it is preferably composed of a material having a 63 Shore D durometer hardness.
The delivery device further can include a prosthesis release component mounted moveably with respect to the catheter to effect a release of the prosthesis from within the catheter lumen. For example, an elongate flexible member, which can be a tube if desired, is disposed inside the catheter lumen and either abuts the proximal end of the prosthesis, or is surrounded by the prosthesis along its distal portion. In many cases the latter arrangement is more desirable, because it enables a retraction of the prosthesis after it is partially deployed, if repositioning is deemed necessary.
The delivery device is particularly well suited for use in a process for deploying a radially self-expanding prosthesis within a body lumen, including:
a. disposing a radially self-expanding prosthesis in a radially compressed state within a catheter, surrounded by a tubular wall of the catheter along a distal end region of the catheter;
b. moving the catheter intraluminally to position the distal end region of the catheter near a selected prosthesis deployment site within a body lumen;
c. with the catheter distal end region so positioned, initiating a release of the prosthesis from the catheter, and during the release, using an optical viewing device to optically view at least a proximal portion of the prosthesis through the catheter wall, to visually monitor a location of the prosthesis; and
d. after completing the release of the prosthesis, proximally withdrawing the catheter to leave the prosthesis disposed within the body lumen.
Thus in accordance with the present invention, a prosthesis can be optically viewed both before its release to insure an accurate positioning within a body lumen, and during its release to monitor its position both with respect to the lumen, and with respect to the delivery/deployment catheter. An endoscope or other suitable optical device can provide an image that enables the user to distinguish among colors, which can be beneficial in recognizing properties of the tissue at the treatment site. Optical images also afford depth of field. The capability of optically viewing the lumen and prosthesis when still contained within the catheter, combined with fluoroscopic imaging of the catheter and the prosthesis, provides particularly effective monitoring of the deployment and positioning of the prosthesis.